Allow egg whites to stand at room temperature for 30 minutes. Meanwhile, lightly grease bottoms of three 8x1-1/2-inch round cake pans*. Line bottoms of pans with waxed paper. Grease and lightly flour bottoms and sides of pans; set aside. In a medium bowl, stir together flour, baking powder, and salt; set aside.

Preheat oven to 350 degrees F. In a large mixing bowl, beat butter with an electric mixer on medium to high speed for 30 seconds. Add sugar and vanilla; beat until combined. Alternately add flour mixture and milk to butter mixture, beating on low to medium speed just until combined.

Thoroughly wash and dry beaters. In a medium bowl, beat egg whites on high speed until stiff peaks form (tips stand straight). Gently stir about 1 cup of the beaten egg whites into batter to lighten. Fold remaining beaten egg whites into batter. Fold in ground pistachios and orange peel. Pour batter into prepared pans.

Bake for 25 to 30 minutes or until cake springs back when lightly touched. Cool in pans on wire racks for 10 minutes. Remove cakes from pans. Cool completely on racks.

Spread White Chocolate Frosting between layers and over sides and top of cake. Just before serving, if desired, top with Caramelized Stars, chopped pistachios, and shaved white chocolate. Makes 16 servings.

White Chocolate Frosting: In a small saucepan, melt 6 ounces white baking chocolate with cocoa butter over low heat, stirring frequently; cool. In a large mixing bowl, beat 1/2 cup butter, softened, and 2 teaspoons vanilla with an electric mixer on medium speed for 30 seconds. Gradually beat in 3 cups powdered sugar. Add 1/3 cup milk. Gradually beat in an additional 3 cups powdered sugar. Beat in melted white chocolate until well combined. If needed, beat in 1 to 2 tablespoons additional milk to make a frosting of spreading consistency. Spread on cake immediately. Makes 3-1/2 cups.

Caramelized Stars: Line a baking sheet with foil; place on a wire rack. Arrange assorted star-shape cookie cutters on foil (six to eight stars ranging in size from 1 to 3 inches across); coat foil and inside of cutters with nonstick cooking spray. In an 8-inch heavy skillet, heat 1/4 cup sugar over medium-high heat until it starts to melt, shaking skillet occasionally to heat sugar evenly. Do not stir. When sugar starts to melt, reduce heat to low. Cook about 2 minutes or until sugar is melted and light golden brown, stirring as needed with a wooden spoon. Immediately and quickly spoon a small amount into each cookie cutter. Cool completely on foil. Gently tap or push stars to remove them from cookie cutters.

*Note: If you don't have three cake pans, chill one-third of the batter while you bake the first two cakes. After removing one of the baked cakes from pan, wash and dry the pan. Prepare pan as directed; bake the chilled batter as directed.

Make-Ahead Tip: If using Caramelized Stars, prepare stars as directed. Store in an airtight container at room temperature for up to 2 weeks. Prepare, bake, and frost the cake as directed. Cover and chill cake for up to 24 hours. Let cake stand at room temperature for 30 minutes before serving.